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NVD / CVE Program· CNA GitHub_M

CVE-2026-33630: c-ares : Use-after-free / double-free in c-ares query-completion handling, remotely triggerable via ares_getaddrinfo() over TCP

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.84% (FIRST EPSS); higher than 57.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: azl3 fluent-bit 3.1.10-6 on Azure Linux 3.0 3.1.10-7.

Low priority for now. Upgrade to azl3 fluent-bit 3.1.10-6 on Azure Linux 3.0 3.1.10-7 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Sep 3, 2026
Updated
Sep 9, 2026
EPSS
0.8% · 57th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • c-ares c-ares

    • >= 1.32.3, < 1.34.7affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10c-aresbefore 1.34.6-2.el10_21.34.6-2.el10_2
AlmaLinux:10c-ares-develbefore 1.34.6-2.el10_21.34.6-2.el10_2
Alpine:v3.21c-aresbefore 1.34.8-r01.34.8-r0
Debian:13c-aresfrom 0—
Debian:14c-aresbefore 1.34.7-11.34.7-1
openSUSE:Leap 16.0c-aresbefore 1.34.8-160000.1.11.34.8-160000.1.1
openSUSE:Tumbleweedc-aresbefore 1.34.8-1.11.34.8-1.1
Red Hat:enterprise_linux:10.2c-aresbefore 0:1.34.6-2.el10_20:1.34.6-2.el10_2
Red Hat:enterprise_linux:10.2c-ares-debuginfobefore 0:1.34.6-2.el10_20:1.34.6-2.el10_2
Red Hat:enterprise_linux:10.2c-ares-debugsourcebefore 0:1.34.6-2.el10_20:1.34.6-2.el10_2
Red Hat:enterprise_linux:10.2c-ares-develbefore 0:1.34.6-2.el10_20:1.34.6-2.el10_2
Red Hat:hummingbird:1c-aresbefore 0:1.34.7-1.hum10:1.34.7-1.hum1
Red Hat:hummingbird:1c-ares-develbefore 0:1.34.7-1.hum10:1.34.7-1.hum1
Rocky Linux:10c-aresbefore 0:1.34.6-2.el10_20:1.34.6-2.el10_2
SUSE:Linux Enterprise Micro 5.3c-aresbefore 1.34.8-150000.3.29.11.34.8-150000.3.29.1
SUSE:Linux Enterprise Server 12 SP5-LTSSlibcares2before 1.9.1-9.24.11.9.1-9.24.1
SUSE:Linux Enterprise Server 16.0c-aresbefore 1.34.8-160000.1.11.34.8-160000.1.1
SUSE:Linux Micro 6.0c-aresbefore 1.34.8-1.11.34.8-1.1
SUSE:Linux Micro 6.1c-aresbefore 1.34.8-slfo.1.1_1.11.34.8-slfo.1.1_1.1

Same product

c-ares: all records

Other highest-scoring records for the same primary product.

  • CVE-2016-5180Heap-based buffer overflow in the ares_create_query function in c-ares 1.x before 1.12.0 allows remote attackers to cause a denial of servic
    42Plan
  • CVE-2025-31498c-ares has a use-after-free in read_answers()
    33Monitor
  • CVE-2017-1000381The c-ares function `ares_parse_naptr_reply()`, which is used for parsing NAPTR responses, could be triggered to read memory outside of the
    31Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2024-25629Feb 23, 2024 · c-ares out of bounds read in ares__read_line()
    22Monitor
  • ← EarlierCVE-2025-62408Dec 8, 2025 · c-ares has a Use After Free vulnerability when connection is cleaned up after error
    23Monitor
  • Later →CVE-2026-69184Sep 18, 2026 · c-ares: CPU-exhaustion denial of service via unbounded DNS name compression pointer chains
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
azl3 fluent-bit 3.1.10-6 on Azure Linux 3.03.1.10-7Microsoft (MSRC)
almalinux:c-ares1.34.6-2.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:c-ares-devel1.34.6-2.el10_2 · AlmaLinux:10Package registry (OSV)
alpine:c-ares1.34.8-r0 · Alpine:v3.21Package registry (OSV)
debian:c-ares1.34.7-1 · Debian:14Package registry (OSV)
opensuse:c-ares1.34.8-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:c-ares0:1.34.7-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:c-ares-debuginfo0:1.34.6-2.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:c-ares-debugsource0:1.34.6-2.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:c-ares-devel0:1.34.6-2.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:c-ares-devel0:1.34.7-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
rocky linux:c-ares0:1.34.6-2.el10_2 · Rocky Linux:10Package registry (OSV)
suse:c-ares1.34.8-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:libcares21.9.1-9.24.1 · SUSE:Linux Enterprise Server 12 SP5-LTSSPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-415 · Double Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records